Actually they are.
I can't find the paper for free, but its called: Canaries in the coal mine: a cross-species analysis of the plurality of obesity epidemics
20.000 animals in 8 different environments are getting fatter. The chance of it not being the same cause is 1/10.000.000.
Edited by BFB, 15 March 2012 - 03:59 PM.